Lord Lexden is the Conservative Party’s official historian. His website can be found here.

The Battle of the Somme, which was to last four and a half months, began on this day one hundred years ago. It was the first serious test of a confident and ambitious new British commander-in-chief on the Western Front, Sir Douglas Haig.

Haig had used all his formidable talents for intrigue to secure the dismissal of his predecessor, Sir John French, a few months earlier. He allowed the politicians no rest until they gave him what he wanted.

The Tories proved particularly susceptible to his persuasive powers. They were to provide him with vigorous support throughout the slaughter on the Somme, for which others criticised him severely, and thereafter until Germany was finally defeated.

Darwen in Lancashire was one among many constituency associations which expressed “the greatest confidence” in Haig “to carry on the war until we have a great victory for Britain and her Allies”.

In the spring of 1916 everything seemed to be set fair. Haig promised the politicians a great success on the Somme. He drew up ambitious and detailed plans for victory.

They were eagerly endorsed by the War Committee of Herbert Asquith’s Coalition Cabinet, formed in May 1915, in which the Tories under Andrew Bonar Law served as junior partners – and the Liberals lost no opportunity of reminding them of their inferior status.

Asquith, one of the cleverest of all Britain’s Prime Ministers, made little attempt to conceal his disdain for Bonar Law. The latter bore the slights valiantly in the cause of cross-party unity which he regarded as essential if the war was to be won. “Everybody says Bonar Law is hypnotised by Asquith”, a Tory cabinet minister noted in July 1916.

Some less emollient senior Tories like Edward Carson, who had led the Irish Unionist resistance to home rule before 1914, demanded a much tougher line with Asquith and pressed for fuller involvement in the making of key decisions. Quite serious internal disagreements were temporarily shelved so that the Party could give wholehearted backing to the Somme offensive.

Haig’s battle plans were wildly optimistic. Everything depended on the success of a sustained, week-long bombardment on the strongly fortified German defensive positions – some 1,500 guns opened fire on June 24.

He believed that after the devastating barrage his infantry would have little difficulty in capturing the Germans’ trenches and breaking right through their lines. The way would then be open for his impressive, well-trained cavalry to sweep the enemy from the towns and villages of northern France.

It quickly became clear that Haig’s immense confidence was misplaced. At least 30 per cent of shells fired by the British guns failed to explode. The shellfire that was successful only managed to penetrate the deep, well-equipped German dugouts on one limited portion of the 18-mile battle front.

On I July the deadly German machine guns were swiftly rolled out to mow down the massed ranks of the British infantry as they advanced slowly, weighed down by equipment. It is for the huge casualties on that terrible first day that the Somme will always be chiefly remembered: 19,240 were killed and 35,494 wounded.

What was meant to be a swift, decisive victory turned into the most bitter and costly of all the battles of attrition fought during the First World War. A hundred years on, the suffering and grief continue to haunt the collective memory of the nation.

When the fighting finally ended on 18 November the British had advanced some ten kilometres at the cost of 419,655 casualties. German casualties were around 600,000.

The Conservative Party in Parliament did not react to these dire events by censuring Haig or expressing deep outrage over the huge loss of life. With over a hundred Tory MPs serving as officers in the armed forces, the Party was immensely receptive to the official briefings provided by the high command.

All reference to the initial high hopes of easy victory disappeared from them. Tories showed a remarkable stoical willingness to accept the inevitability of heavy casualties which Haig naturally now pressed upon them.

George Curzon, who became Leader of the Lords at the end of 1916, said without a flicker of emotion or concern that “if two million(or whatever figure) more Germans have to be killed, at least a corresponding number of Allied soldiers will have to be sacrificed to effect that object”. It is astonishing that any British politician should have used such callous language.

The chief lesson which Tories drew from the Somme was that politicians of all parties needed to show much more vigour and zeal in supporting Haig and his commanders. Munitions and men must be organised and sent – in very large numbers – to the front with the greatest possible efficiency.

To achieve that, they turned the most dynamic individual available, David Lloyd George, who proved an infinitely more congenial Liberal than Asquith. Just over a fortnight after the Somme had ended, Lloyd George became Prime Minister, splitting the Liberal Party in the process.

In the new coalition the Tories, former underlings, became predominant. The Somme did after all achieve something positive: it altered the structure of British politics and in a way that enhanced Britain’s prospects of ultimate victory which the battle itself had not really advanced at all.